The invention relates to an apparatus for folding a gas bag, in particular a side gas bag for a vehicle occupant restraint system, and a method for folding a gas bag using such an apparatus.
Prior to their use gas bags for vehicle occupant restraint systems are usually accommodated in folded form in a housing. The folding is designed such that, on the one hand, the gas bag can be folded in the smallest possible space since the space available is usually limited and, on the other, in the case of restraint the gas bag can be unfolded rapidly and fully when gas flows into it. Because of the precision required for this purpose the folding is frequently work done by hand. Therefore, there is a demand for apparatus and methods which accelerate the folding of a gas bag and, if possible, permit automation.
A method for folding a gas bag is known from DE 197 54 078 A1, in which a gas bag is laid in folds by means of disk pairs successively arranged one after the other, which folds are pushed when the introduction of the disks is terminated. Therefore, as many disks are required as folds are provided. The disks are arranged at a certain distance from one another, which is greater than the distance of the folds in the compressed state in the gas bag housing. The necessary step of pushing together and compressing the folds involves the danger that the precision of folding is reduced.
It is the object of the invention to provide an apparatus and a method for folding a gas bag, by which a gas bag can be folded easily and with precision.
This is achieved in an apparatus for folding a side gas bag for a vehicle occupant restraint system, with a guide channel in which a gas bag to be folded can be disposed, and first and second folding tongues. The folding tongues have teeth and the guide channel has a first side part and a second side part in each of which several recesses are provided. The teeth of the folding tongues are able to engage into the recesses. In this connection, the guide channel which can be made substantially U-shaped serves as a mount for the folds of the gas bag. The gas bag can be folded by the folding tongues, the teeth of which engage the recesses of the side parts. Because of the possibility of moving the teeth of the folding tongues into the recesses of the side parts, the folds in the guide channel can be compressed. Since only two folding tongues are required, the apparatus can be realized simply and in cost-effective manner.
Preferably the first side part extends parallel to the second side part.
The two folding tongues may engage into the guide channel from opposite directions. Preferably, the recesses of the first side part and the recesses of the second side part are arranged staggered.
Advantageously a stop is provided at one end in the guide channel, against which stop the gas bag laid in folds can be pressed for maintaining the folding. To reduce the strain acting on the gas bag, the stop can be biased by a spring.
It is possible to provide a table on which the gas bag to be folded is placed.
The gas bag has a width and preferably the folding tongues extend not over the entire width of the gas bag. This is advantageous in that a gas bag can be provided with e.g. tensioning straps attached to a narrow side of the gas bag before folding. So, the tensioning straps do not come into contact with the folding tongues during the folding due to their reduced width and so cannot be entangled with the folding tongues.
The object of the invention is also achieved with a method for folding a gas bag using an apparatus comprising a guide channel in which a gas bag to be folded can be disposed, and first and second folding tongues. The folding tongues have teeth and the guide channel has a first side part and a second side part in each of which several recesses are provided. The teeth of the folding tongues are able to engage into the recesses. The gas bag is inserted with one end into the guide channel. Alternately the teeth of the first folding tongue engaging the recesses of the first side part and the teeth of the second folding tongue engaging the recesses of the second side part, each of the tongues laying one fold in the gas bag. Each of the folding tongues pushes the fold of the gas bag formed last by the folding tongue towards the fixed end of the gas bag and presses it against preceding folds of the gas bag. Each of the folding tongues after the step of pressing against remains in the guide channel to hold the folds of the gas bag together until the other folding tongue has formed a next fold. Since the folding tongues alternately engage the gas bag and form one fold each per folding tongue, whereupon the respective folding tongue can be pulled back, the number of two folding tongues is sufficient. Since the folding tongues press the just formed fold on the already existing folds, it is superfluous to subsequently push together and press on the folds, which adds to the precision of the folding. The first fold is preferably moved against a stop disposed in the guide channel, which forms a defined abutment surface.
The folding tongue which has laid the last fold can push, when the other folding tongue has been pulled back, all of the formerly laid folds of the gas bag towards the fixed end of the gas bag and can press the folds against it.
The heights of the folds can be determined by changing the insertion length of the teeth of the folding tongues into the guide channel.
Several gas bags can be folded one after another, the folded gas bags remaining in said apparatus while folding a gas bag. This method is particularly effective when the gas bags to be folded each are connected to at least one other gas bag before folding.